The present invention relates generally to apparatus and methods for treating medical conditions, and more specifically, to stent-grafts for use in body vessels to treat those medical conditions.
Stents may be inserted into an anatomical vessel or duct for various purposes. Stents may maintain or restore patency in a formerly blocked or constricted passageway, for example, following a balloon angioplasty procedure. Other stents may be used in different procedures in conjunction with a graft material to form a stent-graft, for example, to hold the graft in an open configuration to treat an aneurysm. Additionally, stents coupled to one or both ends of a graft may extend proximally or distally away from the graft to engage a healthy portion of a vessel wall away from a diseased portion of an aneurysm to provide endovascular graft fixation.
Stents may be either self-expanding or balloon-expandable, or they can have characteristics of both types of stents. Self-expanding stents may be delivered to a target site in a compressed configuration and subsequently expanded by removing a delivery sheath, removing trigger wires and/or releasing diameter reducing ties. In a stent made of a shape-memory alloy such as nitinol, the shape-memory alloy may be employed to cause the stent to return to a predetermined configuration upon removal of the sheath or other device maintaining the stent in its predeployment configuration.
With balloon-expandable stents, the stent may be delivered and deployed using a catheter having proximal and distal ends and one or more balloons disposed on the catheter. The stent may be coupled to the balloon during insertion until the target site is reached, and then deployed by inflating the balloon to expand the stent to bring the stent into engagement with the target site. Alternatively, the stent may be placed separately in the vessel and a subsequent catheter having an expansion portion may then be inserted into the stent to expand the stent at the target site.
Stents also may comprise a variety of configurations. For example, stents may comprise a wire-mesh, coil or helical shape, or a slotted tube configuration. One commonly-employed stent design is known as a “Z-stent” or Gianturco stent. The Gianturco stent may comprise a series of substantially straight segments interconnected by a series of bent segments. The bent segments may comprise acute bends or apices. The stent is arranged in a zigzag configuration in which the straight segments are set at angles relative to each other and are connected by the bent segments.
When stents are employed as part of a stent-graft, the stent commonly is attached to the graft using one or more sutures. Typically, the sutures are hand-sewn around the stent and directly through the graft at multiple locations to secure the stent to the graft. Such suturing techniques may be labor intensive. Further, the formation of suture holes in the graft may increase the risks of endoleaks through the graft, particularly since the size of such suture holes may increase over time.
Various other stent-graft designs have used different techniques to couple the stent to the graft. For example, in some designs the stent may be sandwiched or laminated between two graft layers, where the graft layers are adhered directly to one another to secure the stent therebetween. While such alternative techniques may not puncture the graft, manufacturing complexities may arise and such stent-grafts may comprise an increased profile due to the provision of multiple graft layers.
In view of the above, it would be desirable to provide a stent-graft that secures a stent to a graft, while reducing the likelihood of endoleaks through the graft.